Radio repeater



tors, multiplying stages, etc.

Poema Feb. 1s, 194s UNITED STATES PATENT oFFicE s aamo nErEA'rER.

Bertram Trevor, Riverhead,N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application May`27, 1942, Serial No; 444,649'

6 Claims.

' The present invention relates to radio repeater systems and, more particularly, to a means for controlling the operating frequencies of the radio links in said system. f

An object of the present invention is the pro- 4vision of a radio repeater stationhaving an accurately controlled output frequency. n

Another object of the present invention is the provision .of a repeater station in vwhich the incoming frequency is converted to a lower fre-` quency for amplification and reconverted to a high frequency for retransmission.

A further object of the present invention is the provision of a repeater station,' as aforesaid,

whichrequires only a single local' oscillator for the required frequency conversions.

Another object of the present invention is the` provision of a repeater station, as aforesaid, in which a change of oscillator frequency has no effect in the frequency of retransmission.

Still another object of the. present invention ,is the provision of a relay station which does not require careful balancingof the circuits there- Still another object'of vthe present invention is the provision of a single frequency relay .sys-

`siu a further object is 'the provision of a relay station requiring a minimum amount of auxiliary equipment suchas oscillationgenera- The foregoing objects, and others which may appear from the following detailed description, are attained by the provision of a relay station having a single source of high frequency oscillations which is used at the input of the station to change the received signals to an intermediate frequency and at the output 'to change the intermediate frequency to the frequency of retransmission.

Thel invention will b e more fully understood by reference to the following detailed descrip- I tion, which is accompanied -by a drawing illus'- (ci. 25o-15) frequency F of 400 megacycles, for example, from oscillator I4 are also applied to the converter I2. The 400 megacycle wave may be generated in oscillator I4 or a lower frequency may be gen- 5 erated and higher harmonics obtained through multiplier I3. Oscillator I4 may be either a line controlled orv otherwise stabilized oscillator or it may 'be controlled from a crystal oscillator source.

It should preferably have an output of from 2.

to 3 watts though only a small amount of this Aenergy is used in the converter I2 for converting the incoming signal. The resultant output from converter I2 at a first intermediate frequency of 100 megacycles is applied to an intermediate frequency amplifier I 6. The output from amplifier I=6 is applied -to a converter 20 where it is mixed with theoutput from oscillator I4 and converted to the output frequency F ofv 500 megacycles which is radiated by directive antenna horn- 22 directed toward the next relay station of the system.

It will be noted. that the nrs-t conversion in the station requires-only a small amount of energy from oscillator I'4 and the remainder is used for highlevel conversion in converter 20.

In the foregoing description the frequencies used lwere used only as an illustration and it may, under some circumstances, be more economical from the power standpoint to use a higher intermediate frequency so that the oscillator frequency generated by oscillator I 4 :may be lower and the oscillator, therefore, may be more eilicient.

It should further be noted that in an arrangevention the incoming and outgoing frequencies are identical and are independent of any change in frequency of the local oscillator. If desired, afrequency discriminator and rectifier I'I may be coupled to the intermediate frequency channel at either side of amplifier I6 and the variable direct potential developed thereby utilized as ment constructed according to the present inan automatic frequency controlbias `on oscillator I4. Thus, any shift of the oscillator frequency which would tend to shift the intermediate frequency is counteracted. This may be desirable in wide band transmission in order to A. obviate any vpossibility of side band clipping in amplifier I6 due to frequency shift.

In the arrangement shown in the ligure, the amount of gain which can be used will depend upon the degree of feed back from the transmitting to the receiving antenna. This feed back` .can be reduced by making the antenna directivi-v ties very good as by the use of highly directive' horn antennas, though other wave directive structures may-be used if desired. An adjustable feed back path may be provided such that the amplitude and phase of the feed back energy are equal and opposite to the extraneous space feed back between antennas I and 22. The adjustable feed back path lmay consist of a transmission line or wave guide 24 extending from one antenna to the other or from wave guide or transmission line 2l to wave guide or transmission line Il. Its electrical length is preferably adjustable as shown by the variable dimension line and should be chosen to be as near as possible to the length of the free space feed back pathl between the antennas. An adjustable probe may be provided at each end of the line or guide 24 and extending into guides li and-2| o r into the horns l0 and 22 to allow the amplitude balance to be made or an adjustable amplitude control 25 may be inserted into the wave-guide 24. In some cases, antennas with parabolic reflectors lmay be used.

While I have shown and kparticularly described several embodiments oi' my invention, it is to be distinctly understood that my invention is not limited thereto but that modifications withinl the scope of my invention may be made.

1. A wide band radio relay station having input and output circuits operating to cover the same band of frequencies, -a frequency converter in each of said circuits, a single source of high fre-V quency energy coupled to said converters, a wide band intermediatev frequency channel connecting said input and output circuits and means for obtaining from said intermediate frequency channel a potential variable in polarity and amplitude with departure of lenergy in said channel from a central position with respect to the pass band of said channel and means for utilizing said potential for controlling the frequency of energy supplied by said source.

quency energy coupled to said converters, a wide band intermediate frequency channel connecting said input and output circuits, said single source including a low frequency oscillator and frequency multiplying means between said oscillator and said converters and means for preventing .side band clipping in said intermediate frequency channel, including means for obtaining from said intermediate frequency channel a potential variable in polarity and amplitude with departure oi the mediate frequency of said intermediate irequency band from the midpoint of the pass band of said channel and means for utilizing said of said oscillator.

' l 3. A station as set forth in claim 1 in which 2. A wide band radio remy station having input l each of said circuits. a single source of high frefeed back means are provided between said input and output circuits.

4. A station as set forth in claim, 1 in which feedback means are provided between said input and output circuits, said means including phas and amplitude Aadjusting means.

5. A station as set forth in claim 1 in which feed back means are provided between said input and output circuits, said means including a restricted channel for highfrequency energy. the

a central position with respect to the pass band.

of said amplifier and means for utilizing said potential to restore the energy distribution yin said amplifier to a central position with respect to said pass band, and another wave guide constituting a feed back path between said rst mentioned wave guides. f BERTRAM TREVOR. 

